AU6183473A - Adhesive gun - Google Patents

Description

FORM 4 COMMONWEALTH OF AUSTRALI.

PATENTS ACT 1962-69

Convention, Application for a Patent

NORDSON CORPORATION

61,8 4 n3 Jackson Street, Amherst, Ohio, United States of America

hereby apply for the grant of a Patent for an invention entitled

"ADHESIVE GUN" <11

which is described in the accompanying complete specification. This application is a Convention Application and is based on the application numbered 307,020

for a patent or similar protection made in United States of America

on 16th November, 1972

Or address for service is: Our

Care: SPRUSON FERGUSON PATENT ATTORNEYS ESSO HOUSE, 127 KENT STREET SYDNEY. NEW SOUTH WALES. AUSTRALIA.

Dated this TWElTy'-THIr% day of OCTOBER 19 73

NORDS ORPw ION

Regy: Patent Attorn To: Regitered Patent Attorney The Commissioner of Patents

U

FORM 8 SI COMMONWEALTH OF ALUSTRALIA PATENTS ACT 952-62

DECLARATION IN SUPPORT OF A CONVENTION APPLICATION FOR A PATENT OR PATENT OF ADDITION

In support of the Convention Application made for a

patent for an invention entitled agnftaknetxad&s0in "Adhesive Gun" 61, 8 4 /73

Full name and ad- dress of Declarant. T Eric T. Nord I of 23 Hawthorne Drive, Oberlin, Ohio, USA

do solemnly and sincerely declare as follows:-

1. -4-em-she-applicanc-for-che pa^-_-_dd (or, in the case of an application by a body corporate)

1. I am authorised by NORDSON CORPORATION the applicant for the patent to make this declara- SpxcH1CxakxdktO edbira tion on its behalf.

Insert. country and 2. The basic application as defined by Section 141 of the Act was made ation an'd ame of in United States of America on the foreign apploant. 16 day of November 19 72 by Gerald W. Crum, Eric T. Nord, Simon Tamny and Alan B. Reighard

3.-4-th meeial-.Htnwetor-ef-se-wen-fewed-to-in-the-basie appliestie. (or where a person other than the inventor is the applicant) Full name and ad. dres o iventor(s).3. Gerald W. Crum, Eric T. Nord, Simon Tamny and Alan B. Reighard

of 409 Georgia Ave., Elyria, Ohio; 23 Hawthorne Dr., Oberlin, Ohio; 5320 Longbrook Rd., Lorain, Ohio and 30310 Manhasset Dr., Bay Village, Ohio,respectively, all in United States of America are MaiKthe actual invenror s of the invention and the facts upon which the applicant is entitled to make the application are as follows:

The said applicant is the assignee of the actual inventors. 4. The basic application referred to in paragraph 2 of this Declaration was the first application made in a Convention country in respect of the invention the subject of the application.

I Declared at Amherst,hichis 23rd day of October 19 73

A

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COMMONWEALTH OF AUSTRALIA /I' Form PATENTS 4CT 1952-69 r

COMPLETE SPECIFICATION (ORIGINAL)

1,834 73 FOR OFFICE USE

Class Int. Class Application Number:6. fJ3 '7 -7t'I' Lodged: ,5/0 1

Complete Specification Lodged a45- /0-73 7 Published:/*

Priority 'S I f -7 t2- 2k' v 0 z0

Related Art:iL

7sA.6

Name of Applicant: NORDSON CORP01RaION

Address of Applicant :Jackson Street,, Amherst, Ohio, Unite& States of America

Actual inventorig: GERAlD W. CRUM, ERIC T. NORDr ALAN D. REIGHAR and SIMON -rM~

Address for Service Spruson Ferguson, Patent Attorneys, Esso House, 127 Kent Street, Sydney, New South Wailes, 2000 Australia.

Complete Specific ition for the invention entitled: "ADES ivE GwN

The following statement i~sa full description of this invention, "ncluding the best method of performing it known to mo'ljs

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Abstract of the Disclosure

A thermoplastic material dispensing apparatus

adapted to translate feedstock from a solid state to a

molten state by a novel heater block struicture, and

to discharge the nolten feedstock through a novel dis-

charge valve in response to operation of a novel

trigger device. A novel annular cooling chamber is

established about the dispenser's barrel to maintain

a solid/melt interface inside the barrel adjacent to

the heater block structure, that zone being air cooled

by inlet air uaken from a single inlet air line. The

inlet air f':om the single line also drives the dispen-

ser's ram through use of a novel pneumatic motor/spool

valve mechanism. The spool valve is manually stroked

forward to extend the dispenser's ram for extruding the

feedstock, and is manually stroked rearward to retract

the ram for recharging. Other features include a novel

visual telltale th.t disappears when recharging of the

dispenser is desirable, and a novel safety interlock

that prevents exposure of the charging port for re-

charging unless the dispenser's ram has been fully

retracted and that insures retention of the ram in

that fully retracted position while the charging port

is so exposed.

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To: RegiStered Patent Attorney The Commissioner of Patents

This invention relates to a hand-held,

manually operated dispensing device adapted to trans-

late a solid feedstock into a melt, and to discharge

that molten feedstock when same is desired by an opera-

tor. More particularly, this invention relates to a

hand-held dispenser device especially adapted for use

with a hot mpet adhesive.

In recent years, the use of thermoplastic

materials as adhesives has become quite commonplace

in many industries. Typical of such adhesives is the

so-called "hot melt" adhesive. The hot melt adhesive

is useful in that it provides a strong qui.k setting

bond between workpieces. The quick setting character-

istic derives from the fact that the adhesive melts

or converts to the molten state at a high temperature,

305°F relative to ambient. Because of the large

temperature gradient between ambient and the melt

temperature of the hot melt adhesive, it quickly con-

verts to a solid suate upon exposure to the atmosphere,

thereby providing the rapid bond characteristic. The

quick setting or bonding characteristic of the hot

melt adhesive has opened up multiple and diverse uses

for that type adhesive. For example, it is widely

used in the packaging industry for the erection and

closure of paperbcard cartons, corrugated cartons, and

the like, Further, it is widely used in the furniture

industry in connection with initial construction as

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rc was une nrst application made in a Convention country in respect of the invention the subject of the application.

Declared at Amherst,Ohichis 23rd, day of October 19 73

well as repair. Further, it finds use in the cloth-

ing industry in, for example, the manufacture of rain-

coats, shoes and the like.

A number of hand gun type dispensing devices

are known to the prier art for applying hot melt ad-

hesive to a workpiece. Each such hand gun device is in

the nature of an extruder in the sense that it trap-

lates solid feedstock into melt form, and then discharges

that molten feedstock onto the workpiece as desired by

an operator. Such a dispensing device is generally

referred to as a gun because of its overall similarity

in configuration and operation to a hand gun. That is,

each such hand gun type dispensing device is generally

provided with a pistol grip or handle portion, a gen-

erally barrel-shaped portion within which the feedstock

is melted, and a trigger mechani .a by means of which

feedstock discL rge from the barrel is controlled. Mozi

specifically, a typical hand gun type dispenser for

hot melt adhesive includes a barrel, and a heater block

located at the barrel's fore end. A ram located at

the barrel's aft end forces solid feedstock through

the barrel into proximity with the heater block where

it is turned molten at a solid/melt interface. The

molten adhesive is then directed from the heater

mechanism to a discharge valve/nozzle, discharge of

the molten adhesive being controlled by the gun's

trigger mechanism.

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However, there are a number of problem areas

inherent in fabricating a practical and efficient hand

gun type dispenser device in light of the hot melt

material characteristics and the general abuse and wear

to which guns of this type are put in an operating en-

vironment. These problems are basically associated

with reliability of the device from an equipment per-

formance standpoint under operational conditions.

One major problem area of the prior art

devices concerns the heater block structure, and the

need for efficient heat transfer from the heater block

to the feedstock so as to transform the material from

a solid to a molten state.

Current art principally uses three means of

heating the thermoplastic: a barrel heater located

circumferentially around the exterior of the barrel, a

heated flat plate at the forward end of the barrel

against which the adhesive is forced, an internally

heated torpedo-shaped element located axially within

the gun's barrel, the point or nose of the torpedo

facing the gun's ram; or combinations thereof. In the

case of the barrel heater, thermal energy is transferred

radially into the circumference of the thermoplastic

which then melts and is free to flow back along the

circumference of the thermoplastic toward the ram,

causing sealing and safety problems and tending to lock

up the gun, preventing further advance of the ram and

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thermoplastic. The heated flat plate also suffers

from melt flow-back problems along the circumference

of the thermoplastic and additionally offers a small

heat transfer area to the thermoplast?- requiring a

high power density at the surface with attendant con-

trol and material degradation problems if a high melt

rate is to be achieved. With an internally heated

torpedo the feedstock first contacts the heater block's

nose (which is in the nature of a point) as it is

pres-ed into interengagement therewith by the gun's

ram. If the heaters within the torpedo are operated at

a sufficiently high power level to maintain the temp-

erature of 'he nose above the melting or softening

point of the feedstock, thei the temperature of the

lateral surfaces of the torpedo will be high enough to

char or degrade the feedstock material. Conversely,

if the heater power level is reduced to bring the

lateral surface temperature down to a safe level, then

the poor heat transfer geometry of the torpedo will

allow the nose temperature of said torpedo to drop

below the softening or melting temperature of the feed-

stock and thereby prevent further advance of the

feedstock and ram.

The initial contact heat transfer problem

multiplies the problem of controlling the solid/melt

interface within the gun's barrel so as to prevent

the molten material from moving rearwardly into the

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gun barrel's charging port area. If the solid/melt

interface is not maintained closely adjacent the

torpedo's nose, the gun's ram may wcll becume hung up

or stuck within the gun barrel so as to preclude fur-

ther use of the gun prior to disassembling and cleaning.

Another major problem area of the prior art

devices concerns the mechanics of operating the gun, and

the disadvantages of those mechanics from an equipment

maintenance standpoint. For example, most prior art

trigger mechanisms (and, therefore, most prior art

discharge valves) can be overloaded past the breaking

point by an operator an restart if the thermoplastic

remaining in the gun has not reached a molten state.

Oftentimes, an operator tends to feel that any operat-

ional problem with a gun of thi.s general type can be

corrected simply by pulling or depressing the trigger

as hard as is humanly possible, until the gun breaks.

A further problem in connecction with the guns

of this type arises in connection with retraction of the

gun's rar, after a feedstock cliarge has been fully ex- pended, or after the ram becomes stuck intermediate

in its stroke from fully charged to fully exhausted

positions. Cenerally speaking, in most prior art

devices the gun's ram is not positively dr4.ven in both

the forward and reverse directions; most often the

gun's ram is pos~itively driven in the eject direction

but is only spring loaded in the retract direction.

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If the gun's ram becomes bound within the barrel, it

is often the case that the spring loading is not

sufficient to overcome that binding. This means the

gun must be disassembled for cleaning.

Further, none of the examples of current

art use a melt piessurization system capable of generat-

ing large axial forces. Experiment has shown that

large forces, translated into high fluid pressures in

the range of 300 pounds per square inch at the solid/

melt interface, are necessary to move the melted feed-

stock out of the solid/melt interface since a layer of

fluid remaining at the solid/melt interface serves to

insulate the solid from the melted, limiting the melt

rate. Such high forces will, of course, further inten-

sify the melt back or leakage problem. Lack of a means

tc generate these high pressures tends to limit current

art devices to either low melt rates, or to materials

which have low viscosity when melted.

Still a further major problem area of the

prior art devices concerns safety hazards, and lack of

operational indicators, from an operator's standpoint.

Feed charging ports found on guns of this type open

directly L.co the gun'o barrel and, thereby, directly

expose an operator's fingers to the gun's ram. Of

course, such provides a distinct safety ?roblem to the

operator unless there is some kind of an interlock

between the barrel's charging port and the motor drive

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for the gun's ram. Further, guns of this type do not

include a telltale device by which an operator can

visually observe at a glance when the gun's barrel needs

recharging with feedstock. Such, of course, is un-

desirable from an operator's standpoint in that he must

be constantly checking the feedstock level by opening

and closing the barrel's charging port, thereby ex-

posing his fingers, etc. to the potential safety

hazards.

Generally speaking, it has been a primary

objective of this invention to provide an improved

hano gun type thermoplastic dispensing device that is

particularly adapted for use with a hot melt adhesive.

Another objective of this invention has been

to provide an improved heater block structure for use

in thermoplastic material dispensing systems. In that

regard, the heater block structure of this invention

is in the nature of a tapered surface disposed axially

within the gun's barrel, the tip of the tapered sur-

face facing the gun's ram. An annular chamber is

defined around the exterior of the gun's barrel just

aft of the tip of the tapered surface, that chamber

being ported to admit inlet air over a pressure drop

so as to provide substantial cooling of the barrel at

that location, thereby maintaining the solid/melt

interface of feedstock adjacent to the heater block.

The cooling air from within the annular chamber is exhausted forward around the barrel toward the heater block to secure additional cooling of the barrel.

It has been another objective of this in-

vention to provide an improved trigger mechanism for a

hand gun type device adapted to dispense a thermoplastic

material, a hot melt adhesive. The improved

trigger mechanism is structured to prevent operator

breakage of the melt discharge valve no matter how hard

the trigger is pulled. In accomplishing this object-

ive, the discharge valve is adapted to linearly recipro-

cate iii opening and closing a discharge orifice. The

valve stem abuts against, but is not connected to, a

spring loaded abutment that is reciprocable in a linear

direction on the valve's linear reciprocation axis.

The trigger is interconnected by a lost motion connect-

ion with the spring loaded abutment. When the trigger

is led, che spring loaded abutment is retracted

from interengagement with the valve, thereby allowing

the valve to open for discha.rge of melt. The valve

opens when the abutment is retracted only because of

the melt's hydraulic pressure, it is not mechan-

ically drawn open through a trigger connection. That

is, the valve is configured so that hydraulic pressure

from the melt causes it to open after the abutment

has been withdrawn by the trigger against the bias of

its spring loading. When the trigger is released, the spring loaded abutment biases the valve closed. Thus, the discharge valve cannot be overloaded (and, there- fore, cannot be broken or otherwise adversely affected) by an operator through pulling hard on the trigger since pulling the trigger only releases an abutment from contact with the valve, the valve itself being opened by hydraulic pressure of the melt.

The lost motion characteristic of the trigger

attachment to the spring loaded abutment prevents the

valve from being held closed if the hydraulic pressure

acting on the bellows is sufficient to overcome the

bias of the spring. Thus, the valve is self-relieving

and acts to protect the device from excessive internal

pressures.

It has been still another objective of this

invention to provide a novel control valve and pneumatic

motor for operation of the ram in a hand gun type de-

vice adapted to dispense thermoplastic material, e.g.,

a hot melt adhesive. The control valve includes a

spool valve axially aligned with the travel path of

the gun's ram. The spool valve's porting is arranged

so stroking the spool valve forward along the gun's

housing by an operator allows the pneumatic motor to

drive the ram forward for melt discharge, and stroking

the spool valve rearward along the gun's housing allows

the pneumatic motor to drive the ram rearward for recharging the feedstock. The spool valve is struct- ured to admit pneumatic pressure onto both sides of the motor's piston head, and is also configured to allow exhausting of the air from both sides of the motor's piston head, depending on which side is under positive pressure, depending on whether the ram is being driven forward or rearward.

The pneumatic motor is designed to have a

large ratio of piston to ram area allowing large axial

forces, and therefore hydraulic pressures, to be gen-

erated with low air pressures.

It has been a further objective of this in-

vention to provide safety structure in combination

with the charging port for the extruder barrel in a

hand gun type cevice adapted to extrude a thermoplastic

material, a hot melt adhesive. That safety

structure prevents recharging of the barrel unless

the gun's ram is restrained in its fully retracted

position. In one embodiment in which the gun is adapted

to use granular feedstock, the hopper's lid is pivot-

ally mounted relative to the gun's housing., The lid

carries an extension which is movable into and out

of the gun's barrel, iu~o and out of the ram's

path when the ram is fully retracted, to function is

a safety stop on the ram. Since the lid's extension

can move into the gun's barrel only when the ram is

retracted, the hopper's lid can only be opened at that time. When the gun's ram is fully or partially extended, the hopper's lid cannot be opened because the lid's extension interengages the ram as attempt is made to move it into the barrel.

It is still a further objective of this in-

vention to provide indicator means for a hand gun type

device adapted to extrude a thermoplastic material,

a hot melt adhesive, that visually indicates at

a glance when recharging of the gun's barrel with

additional feedstock is desirable. Toward this end,

a telltale rod is aligned axially with a piston that

powers the gun's rata, the telltale rod having an end

that protrudes through the gun's housing when the gun's

barrel is fully charged so as to visually indicate that

status to the operator. The telltale rod slides

axially relative tc the piston, and is adapted to be

picked up by the piston when the gun's ram approaches

the fully extended position. Therefore, as the ram is

extended (due to discharge of molten feedstock from the

gun), the telltale rod is withdrawn into the interior

of the gun. When the telltale rod fully disappears

into the gun, such indicates recharging of the gun's

barrel with additional feedstock is desirable.

Other objectives and advantages of this in-

vention will be more apparent from the following de-

tailed description taken in conjunction with the

drawings in which:

T u

Figure 1 is a cross sectional view taken

axially of a hand gun adapted to extrude a thermo-

plastic material a hot melt adhesive) structured

in accord with the principles of this invention;

Figure 2 is a cross sectional view taken

along line 2-2 of Figure 1;

Figure 3 is a cross sectional view taken along

line 3-3 of Figure 1 showing a hopper structure for

powder or pellet type feedstock;

Figure 4 is a cross sectional view similar to

Figure 3 but showing the gun's hopper lid in the open

or charging attitude;

Figure 5 is a vertical cross sectional view

taken along line 5-5 of Figure 1;

Figure 6 is a partially broken away cross

sectional view similar to Figure 1 but showing the

gun's ram in an intermediate extended attitude;

Figure 7 is a cross sectional view similar

to Figure 6 hut showing the gun's ram in the charging

attitude;

Figure 8 is a cross sectional tiew similar

to Figure 1 showing an alternative embodiment of the

gun's discharge valve structure;

Figure 9 is a cross sectional view similar

to Figure 3 showing an alternative cover structure for

a slug type f edstock where the gun is adapted to carry

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only one slug at a time, the cover structure being

shown closed in solid lines and open in phantom lines;

Figure 10 is a cross sectional view taken

along lines 10-10 ,f Figure 9;

Figure 11 is a cross sectional view similar

to Figure 9 showing another alternative cover structure

for a slug type feedstock where the gun is adapted to

carry multiple slugs; and

Figure 12 is a cross sectional view taken

along line 12-12 of Figure 11.

General Structur" and Operation

The general structure of a hand gun type

device adapted to dispense a thermoplastic material,

a hot melt adhesive, in accord with the principles

of this invention, is illustrated in the Figures.

As shown in Figure 1, the hand gun 10 includes

a housing 11 having a generally barrel-shaped portion

12, and a pistol grip type handle portion 13 depending

from the underneath side thereof. A cylindrical barrel

14 is located inside the gun's housing 11, the barrel's

axis 15 being substantially parallel to the axis of the

housing's barrel portion 12. The barrel 14 is seated,

as at 16, ir.a heater block structure 17 at the fore

end 18, and receives an axially movable ram 19 at the

aft end 20. The cam 19 is driven fore and aft, i.e.,

is extended and retracted in a positive manner, but a

pneumatic motor 30 that is controlled through use of a spool valve 31. A telltale rod 32, cooperatively interconnected with the ram 19 through the motor's piston head 104, indicates when recharging of the barrel

14 with additional feedstock is permitted.

The barrel 14 is charged with feedstock (of

either powder, granules, or slug characteristics) through

charging port 21 located topside of the barrel just

forward of the ram 19 when the ram is fully retracted

as shown in Figure 1. When powder or granular feed-

!0 stock 24 is used, a hopper 22 with safety lid 23 is

mounted to cooperate with the charging port 21. Wheq

slug feedstock 25 is used, either a safety cover 26 is

mounted to cooperate with the charging port 21 when

the gun 10 is adapted to receive only one slug at a time

(see Figures 9 and 10), or a slug tur:et 27 is mounted

to cooperate with the charging port 21 when the gun is

adapted to carry replacemen slugs, too (see Figures

11 and 12).

A discharge valve 28 is located at the fore

end 18 of the barrel 14, the discharge valve control-

ling discharge of molten feedstock through nozzle 29.

Molten feedstock is transferred under hydraulic press-

ure from the barrel 14 to the discharge valve 28 through

bores 33 in the heater block 17. The discharge valve

28 is actuable by an operator through use of a trigger

assembly 36.

In use, the barrel 14 is first charged with

feedstock while the ram 19 is fully retracted, see

Figure 1. Such charging can be accomplished only when

ram 19 is fully retracted because of safety structure

23, 26 or 27 (depending on whether powder, granular or

slug feedstock is used) associated with the barrel's

charging port 21. Heat is introduced into the heater

block 17 by energizing a switch (not shown), and high

pressure air is introduced into first air chamber 34 by

stroking handle 35 on spool valve 31 (and, hence, the

spool valve itself) forward toward the gun's nozzle

29 (see Figure Such forces the feedstock against

the heater block 17 where it is melted, and forces the

feedstock through bores 33 into discharge valve 28.

When desired by the operator, discharge valve 23 is

opened by pulling on trigger 37, thereby discharging

the desired quantum of melt through nozzle 29. When

recharging of the barrel 14 is desired, high pressure

air is transferred into second air chamber 38 by strok-

ing handle 35 on spool valve 31 rearward toward the tail

end of the gun's housing 11. Such returns the ram 19

to the charging position shown in Figure 1 from a dis-

charge position such as shown in Figure 6.

General Design of Heater Structure

With reference to Figures 1, 2, 6 and 7 of

the .drawings, it should be noted that the specific

geometric design of the projection 44 of the heater block 17 is illustrated as a truncated right circular cone. However, the special physical characteristics inherent in this design can be met by several topologic- ally similar geometries, such as:

T'e heater block 17 should have a heated

base 43; the projection 44 is not inter-

nally heated but provides a heat transfer

path from the heater base 43 through the

projection 44 into the surrounding medium

to be heated.

The truncated projection 44 has a continu-

ous but not necessarily linear or axi-symmet-

ric taper from its base to the opposite end

thereof, cone, pyramid, paraboloid,

both regular and irregular, and annular

or hollow centered version thereof.

The projection 44 should have a geometry

which tends to physically force the material

in a generally radially outward direction

against the cooled barrel 14, thereby

facilitating a seal and allowing the flow of

molt ,n material from its tip to the base end

of the projection rather than impede or

restrict it.

The barrel 14 is deliberately cooled to

establish a large axial thermal gradient

upstream of the heater block 17. This is in order to chill and solidifp the melted material forced outward by the center pro- jection, thus forming a seal. Further, the cooled barrel prevents premature melting of the solid material.

Thermal Characteristics of Heater

The tapered member, projection 44 of Figures

1, 2, 6 and 7, is designed to have certain specific

heat transfer properties which must be present in

combination in order to operate successfully as a

thermoplastic melter at the design melt rate.

The total heated surface 47 and 48 exposed

to the thermoplastic must be great enough

to keep the power density below the point

at which surface temperatures induce charring

or other degradation of the feedstock when

melting at the design rate.

The material selected for the projection 44

must have a sufficiently high thermal con-

ductivity such that when transferring the

required thermal energy from the heater

block 17 to the tip surface 47, the tempera-

ture drop incurred does not allow the tip

surface 47 temperature to go below the soft-

ening point of the feedstock.

The length of projection 44 between the

heater block 17 and the tip 47 is coordinated with the base diameter D' and tip diameter

D to obtain the required surface area of

paragraph a) above and within the allowable

maximum temperature drop of paragraph 9)

above.

Specific Structure

In connection with the heating and cooliig

structure and discharge valve 28, note particularly

Figures 1, 2, and 6. As shown therein, the heater

structure is in the nature of a heater block 17 having

a base 43 and a frusto-cone 44 integral with the base.

Note that the flat face 47 of the frusto-cone 44 is

oriented transverse to the barrel's axis 15, that the

frusto-cone's axis is the same as the barrel's axis

that the minor face 47 of the cone faces the ram 19, and

that the frusto-conical side 48 is substantially straight

from the face 47 to the base 43. Instead of being

straight sided 48, the sides of the frusto-cone may be

slightly convex or slightly concave if desired. Prefer-

ably the major cone diameter D' is substantially the

same as the barrel's inside diameter.

A frusto-conical configuration is used for

the heater block 17 because it has been found that

same provides optimum heat transfer characteristics

for melting a solid thermoplastic material such as a

hot melt adhesive in a hand gun type dispensing device.

It is desired from a heat transfer standpoint that

the entire heater block 17, and especially the frusto-

cone 44, be formed of copper because of its optimum

properties in connection with heat transfer; however,

aluminum or silver may be used, too. At relatively

high operational temperatures, it may be desirable to

nickel-plate the copper's exposed faces because of

copper's tendency to promote degradation of certain

types of hot melt adhesives. Thus, the exposed sur-

faces of the frusto-cone may be provided with a nickel-

plate on the order of .0003 to .0005 inch so as to take

advantage of the good thermal transfer of copper while

substantially negating the negative characteristics

of the copper; this thickness is not critical so long

as it is thin enough that cracking or flaking does not

occur.

The base 43 of the heater block 17 is pro-

vided with two electrical resistance type heater ele-

ments 45 slip fit into bores 46, thereby providing the

entire interior volume of the frusto-cone for heat

transfer from the base 43 to the cone's flat face 47

and side wall 48. This establishes an efficient way

of transferring heat to the frusto-cone's surface in-

side the barrel 14 without creating hot spots on that

surface. Further, this heater block 17 structure by

virtue of the high thermal conductivity of its material allows single point temperature control for the whole heated section of the gun, zone controls at different locations in the heater block 17 and/or barrel 14 are not necessary or desirable. The heater elements 45 are connected by suitable wiring, not shown, with power cord 49 in the gun's handle 13.

The base 43 of the heater block 17 is also

provided with a longitudinal valve bore 50 having axis

53 that is parallel with the axis 15 of the frusto-

cone 44 and barrel 14. This valve bore 50 is connected

by main transfer bore 33 with the barrel 14, the bore

33 being of inverted Y-shaped configuration with arm

33a communicating with the upper portion of the barrel,

and arr 33b communicating with the lower portion of the

barrel, to prevent melt hangup in either the top or

bottom of the barrel. The heater elements 53 are dis-

posed on each side of the transfer bore 33 and valve

bore 50. Molten feedstock is drained from the barrel

14 through port 51 adjacent the top of the barrel and

through port 52 adjacent the bottom of the barrel, both

of these ports being disposed adjacent the base of the

frusto-cone 44. Since melt transfer bore 33 and dis-

charge bore 50 are defined in the heater block 17 it-

self, and since the base 43 thereof is of substantial

bulk relative to the volume of the bore 33, it will be

understood that the molten feedstock is maaintained at

a substantially constant temperature as it is

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transferred from the barrel 14 to the nozzle 29.

The cooling structure is in the nature of an

annular cooling chamber 90. The cooling chamber is

disposed coaxially with barrel 14 on the outside thereof

just aft of the frusto-cone's face 47, see Figure 1.

The cooling chamber 90 cooperates with a coolant dis-

tribution bore 91 that runs axially of the housing

beneath the barrel 14. The distribution bore 91 commun-

icates at one end through pressure drop port 92 with

tile cooling chamber 90, and intermediate thereof with

threadnd coolant inle" port 93. Inlet air supply line

94 extends through handle 13, and is threaded into

port 93 and retained in operative combination there-

with by nut 95. The distribution bore 91, at that end

opposite the cooling chamber 90, opens onto an annular

manifold chamber 96 through port 97.

The cooling chamber's pressure drop port

92 is especially sized, relative to the distribution

bore 91, to provide metered flow of air from the bore

91 into the cooling chamber. Such is desired because

of the maximum cooling effect created by an adiabatic

expansion of the air on the barrel's outer surface

as the air passes from a high pressure to an atmos-

pheric pressure state (the cooling chamber 90 is at

substantially atmospheric pressure because same is

open through porting explained below to the gun's

operating environment). The cool air so created by the pressure drop, and the concentration of that cool air in an annular ring just aft of the heater block's frusto-cone 44, controls the situs of the solid/melt interface 102 within the barrel 14 at a certain location interiorly of the cooling chamber and prevents that interface from moving aft towards the barrel's charging port 21. Because the solid/melt in- terface 102 is maintained with certainty inside the barrel 14 during use of the gun, the length of the barrel can be shortened to a minimum since no melt back of the interface occurs along the barrel; this allows a short length feedstock charge (whether pellet or slug) to be used and, thereby, lessens the mechanical work required by the ram motor 30 to push the charge through the barrel.

In the case of a pelletized or granular feed-

stock, t:he material shows considerable tendency to

expand radially when subjected to an axial force, caus-

ing substantial friction between the barrel and feed-

stock. Since this friction force is an exponential

function of charge length, it is desirable to keep this

length as short as possible.

Note that the barrel 14 is partially supported

by annular rib 98 which defines the aft face of the

cooling chamber 90. Note also that annular rib 99

which defines the fore face of the annular cooling air

chamber is slightly spaced from the outer periphery

of the barrel, thereby providing an annular port 100 which directs the cooling e.ir axially forward along the exterior surface 18 of the barrel 14 to aid in the cooling of the barrel 14 and in the establishment of a large axial thermal gradient in the barrel 14 in the area adjacent to the frusto-cone 44.

The discharge valve 28 includes a valve stem

and a valve head 56 w'thin valve bore 50, the valve

head being adapted to seat against a valve seat 57 in

sealing fashion. The valve seat 57 may be press fit or

cast into the heater block's base 43, and the nozzle 29

is threaded into the seat 57. The nozzle's discharge

bore 58 is axially aligned with the valve bore 50 and

stem 55, and with hole 59 defined in the valve seat

57. A static seal in the nature of a compressible bell-

ows 60 is fixed at one end 61 to the valve stem 55 ad-

jacent the valve head 56, and is fixed at the other end

62 to the inner periphery 63 of a donut-shaped retainer

ring 64 fixed to the heater block's base 43. The

bellows seal 60 functions to allow axial movement of

the valve stem 55 (and, hence, of the valve head 56)

on and off the valve seat 57 as allowed by the trigger

assembly 36, while maintaining a seal to prevent leak-

age of molten feedstock through the aft end of the valve

bore

The valve head 56 is hydraulically unbalanced

(note tapered face 65 of the head 56 that flares away

from seating face 66 of the seat 57) such that the valve head and stem 55 will move rearwardly as viewed in Figure 6 when no major compression spring 68 loaded abutment 69 is presented against the aft end 67 of the valve stem. Once the hydraulic pressure on tne feed- stock (as established by the ram 19) is sufficient to move the valve head 56, such rearward motion of the valve head allows molten feedstock to be discharged through the nozzle 29.

While the valve head 56 is hydraulically

unbalanced relative to tae valve seat 57 so that same

moves axially rearward, so that the discharge

valve opens, when the molten feedstock achieves a high

enough hydraulic pressure, it may be desirable to

provide a mechanical assist for opening the discharge

valve. Such an assist can be established by stretch-

ing the bellows seal 60 on the order of .010 to .015

inch before assembly of the discharge valve 28, thereby

giving it the characteristics of a tension spring as

well as that of a seal. In this attitude, the bellows

seal 60 itself, in combination with hydraulic pressure

on the molten feedstock, functions to lift the valve

head 56 from the seat 57 when the spring 68 loaded

abutment 69 is removed from the valve stem's aft end

67.

Another structure for providing a mechanical

assist in lifting the valve head 56 off the valve

seat 57 is shown in Figure 8. This alternative pro-

vides minor compression spring 70 which bears against flange 71 fixed to the valve stem 57 at one end and against the fixed retainer ring 64 at the other end.

In other words, minor compression spring 70 partially

opposes major compression spring 68. When the major

spring 68 loaded abutment 69 is removed from the valve

stem's aft end 67 in this embodiment, spring 70, in

combination with hydraulic pressure of the molten feed-

stock, functions to lift the valve head 56 from the

seat 57.

Another device to assist in lifting the valve

head 56 cff the valve seat 57 can be provided by a

spring loaded mechanical catch which will engage a pro-

jection on the valve stem 67 near the end of travel of

trigger 37. Said spring is designed to be strong

enough to overcome resistance of the valve stem 53 but

not so strong as to allow damage to the valve components.

The gun's trigger assembly 36 is particularly

illustrated in Figures 1 and 5. The trigger 37 is

adapted to cooperate with the major spring 68 loaded

abutment 69. The trigger 37 functions only to with-

draw the abutment 69 against the spring 68 bias, there-

by allowing the discharge valve 28 to open due to

hydraulic pressure of the molten feedstock only (or as

assisted by placing the bellows seal 60 in tension or

by the minor spring 70 structure shown in Figure 8).

The spring 68 loaded abutment 69 is in the nature of a cup 74 within which the valve stem 55 is slidingly received, the stem's aft end 67 abutting the cup's floor when the discharge valve 28 is closed. The cup 74 is mounted on a shaft 76 which is slidingly received in bracket 77, the bracket being fi a fixed or immobile position. The bracket 77 defines a well 78 within which the major compression spring 68 is seated, the spring 68 bearing against the underside of the cup 74 so as to continuously urge same forward toward the nozzle 29, so as continuously to bias the dis- charge valve 28 toward the closed attitude where valve head 56 is seated on valve seat 57.

The trigger 37 extends through slot 79 in

the housing 11, the trigger being protected against in-

advertent contact in the usual manner by trigger guard

formed integral with the housing's barrel portion 12

and handle 13. The trigger 37 is mounted to the base

of an oval yoke 81 that surrounds the barrel 14, see

Figure 5. A thumb 82 extends up from the oval yoke 81

into proximity with the reciprocable abutment's bracket

77. The trigger's thumb 82 defines an elongated slot

through which the abutment's shaft 76 passes, a

plate 86 being fastened onto the shaft 76 so that the

trigger's thumb is captured on the shaft 76 between

the plate and the bracket 77. Hence, the trigger 37

itself simply hangs on, is not directly connected

to, the abutment's shaft 76. This lost motion kind of

-28- L .J I.

r l

connection eliminates potential binding of the shaft

76 within the bracket 77 as the shaft reciprocates

linearly therein in response to trigger operation.

Binding of the shaft 76 within bracket 77 would be

normally expected to occur if the trigger 37 were

directly conLected to the shaft 76 since the trigger

moves in an arcuate path as opposed to the shaft's

linear path.

To remove the cup-shaped abutment 69 from

contact with the valve stem's aft end 67 (so that the

discharge valve 28 can open), the trigger 37 is pulled

rearwardly by an operator's index finger, causing the

trigger's thumb face 83 to bear against aft face 84 of

the abutment's bracket 77, thereby causing the cup 74

to be drawn rearwardly against the bias of compression

spring 68 since the trigger's thumb 82 is captured on

the abutment's shaft 76 and bears against the plate

86. When the operator releases the trigger 37, com-

pression spring 68 moves the cup 74 into abutting con-

tact with the valve stem 55. Since compression spring

68 is qutte strong relative to the opening forces

(hydraulic and/or spring) on the valve head 56, the

discharge valve 28 is closed when the trigger is re-

leased. Because there is no positive mechanical

connection between the trigger assembly 36 and the

discharge valve 28, no matter how hard an operator may

depress the trigger 37 it will not cause any mechanical

-29-

"'1 structure to bear on the discharge valve itself.

The pneumatic motor 30 is, in essence, a

piston head 104 fixed to and molded integral with the

ram 19. The ram and piston head are fabricated of a

thermally conductive material, thereby providing an

efficient heat transfer path for conduction of heat

away from face 107. The pistua head 104 is located

within motor chamber 105, that chamber 105 being divided

into first sub-chamber 34 and second sub-chamber 38 by

the piston head. 0-ring 106 on the outer peripuery of

the piston head 104 insures the integrity of the sub-

chambers 34, 38 one from the other. The ram 19 itself

defines a hollow interior 136 that is continually

opened to sub-chamber 34 through port 205 in piston

head 104. This allows an additional degree of cooling

to be achieved throughout the ram's length, and particu-

larly at the inside face 201 of the ram, since the com-

bination of the ram's linear reciprocatory motion

within chamber 105 and pressurized inlet air within

sub-chamber 34 introduces an air flow within the ram's

interior. Of course, the exterior of the ram 19 is

provided with a degree of cooling through the air flow

within sub-chamber 38.

A solid ram 19 would allow superior conduct-

ion of heat away from face 107; however, a hollow ram

19 is illustrated in Figures 1, 6 and 7 so as to pro-

vide space for the telltale indicator 32.

I

7 w

Note that the ran 19 and piston head 104 are

axially aligned with the barrel 14. Thus, air pressure

on face 111 of the piston head 104 extends the ram 19

toward the heater block 17, and air pressure on face 112

of the piston head retracts the ram away from the heater

block 17, with no loss in mechanical energy transfer

from the piston head to the ram. Note also that the

outside diameter W of the ram 19 is substantially

identical to the inside diameter W' of the barrel 14,

the ram thereby acting as a closure for the barrel's

charging port 21 as the ram is extended through the

barrel. Note also that the axial length L of the ram

19 is not as great as the length L' of the barrel 14

between the ram's face 107 and the frusto-cone's face

47 when the ram is fully retracted as shown in Figure 1.

This, of course, prevents the ram's face 107 from con-

tacting the frusto-conical heater's face 47 when the

ram 19 is fully extended. When fully extended, the

stop flange 108 on the ram 19 engages plate 109 (which

forms one side face of the control air chamber 96) to

form a positive limit stop on the ram's forward motion.

Further, the motor chamber 10'i is providuJ with an

annular rib 103 adapted to funccion as an aft stop for

the piston head 104, for the ram 19, when it is

in the fully retracted position shown in Figure 1.

Note also that the area of piston head 104 is sub-

stantially larger than the area of ram face 107 acting

-31-

i to form a pressure intensifier and allowing the genera- tion of large unit pressures at ram fact- 107 from low pressure plant air supplies.

The piston head 104 and ram 19 may be formed of

a high heat conducting material such as aluminum, if

desired. Such promotes heat transfer away from the ram's

face 107 back along the ram where it can be dissipated

through the inlet air circulating inside and outside of

the ram in motor chamber 105. Ho ev'r, the piston head

104 and ram 19 also may be formned of a molded plastic if

desired. This is because of the cooling provided for

the barrel 14 aft of the frusto-cone 44 by the exhaust

air from the cooling chamber 90, and because of the

interior and exterior cooling of the ram 19 through the

ram motor 30. It should be understood that a ram of

plastic or other thermally nonconductive material limits

the useful upper operating temperature of the device and/

or the allowable closeness of approach of ram face 107 to

face 47 of the heater. However, if the ram 19 is formed

of a plastic, and especially in that embodiment where a

hopper 22 for powder or pellets is used, it is desirable

that the outer periphery of the ram's face 10 be provided

with a steel ring insert 110. This steel ring insert 110

functions to shear off any pellets or granules hung up in

the charging port 21 as the ram 19 progresses from the

fully retracted attitude illustrated in Figure i toward

an extended attitude illustrated in Figure 6. In the

hopper 22 embodiment, note that the charging port 21 is circular in configuration, and that the ram's face 107 is transverse to the barrel's axis, thereby minimizing the shearing force required since only a few such pellets will be sheared off at a time; this aids in prevention of ram 19 hang up or sticking in the barrel 14 as it is extended forward.

A control valve in the form of a spool valve 31

is provided for the pneumatic motor 30. The spool valve

31 is interposed between the manifold chamber 96 and the

motor chamber 105 along the top of the gun housing s

barrel portion 12, see Figure 1. The spool valve 31 is

adapted to slide axially within spool valve bore 113,

that bore having an axis 114 disposed parallel to but

spaced from the ram and barrel's axis 15. The spool

valve includes a lip 115, 116 at each end thereof, the

annular periphery of each lip being provided with an

0-ring 117 to maintain operating pressure and integrity

between the manifold chamber 96, and between the two sub-

chambers 34, 38 of the motor chamber 105. Port 118

interconnects one end of the spool valve bore 113 with

sub-chamber 34 of the motor chamber 105, and port 119

connects the opposite end of the spool valve bore with

sub-chamber 38 of the motor chamber 105. Transfer bore

120 extends axially of the spool valve 31 from one end

thereof to the other. The transfer bore 120 serves to

interconnect the manifold chamber 96 (through port 121 in plate 109) with the sub-chamber 34 of motor chamber 105 through port 118 when the spool valve 31 is oriented as shown in Figure 1, thereby allowing the ram 19 to be extended toward the heater block 17. The manifold chamber 96 is exposed to sub-chamber 38 of the motor chamber 105 through port 119 when the spool valve is positioned as shown in Figure 7, thereby allowing the ram 19 to be retracted into the charging attitude.

The control valve's handle 35 is mounted on

the spool valve 31 through slot 122 in the spool valve's

housing 123, that interconnection being accomplished by

use of web 124. Hence, an operator causes ram 19 to

exte!Ld by stroking spool valve 31 forwardly through use

of handle 35 when high pressure air is applied to

manifold chamber 96. Conversely, an operator causes

ram 19 to retract by stroking spool valve 31 rearwardly

through use of handle 35. Thus, the control valve for

thc pneumatic motor is oriented so that forward motion

of the handle 35 extends the ram 19 into a pressurized

condition and rearward motion of that handle 35 retracts

the ram into a feedstock charging position, thereby

making operation of same readily -and easily understand-

able to the operator.

The telltale rod 32 is slidingly received

within telltale bore 127 formed in the motor chamber's housing 128, that bore 127 being coaxial with the axis of the ram 19 and barrel 14. O-ring 206 is provided to prevent leakage of air from sub-chamber 34 to the environment through that bore 127. The telltale rod 32 also extends into the hollow interior 136 of the ram 19.

The telltale rod 32 is adapted to move between an outer

position (shQwn in Figure 1) where tip 129 thereof is

visually exposed to an operator and an inner position

(shown in Figure 6) where tip 129 is removed frum the

operator's vision. As mentioned, when the telltale

rod's tip 129 is retracted into the housing, the operator knows it is time to recharge the barrel 14.

The telltale rod 32 comprises a four-part stem,

the aft section 130 carrying the visual indicator in the

form of tip 129. The intermediate section 131 provides

a stop lip 132 which limits the telltale rod's outward

motion in direction 133, that lip 132 abutting against

annular collar 134 when the rod 32 is fully extended as

shown in Figure 1. The guide section in the form of a

circular plate 135 is axially mounted on the rod 32

between the intermediate section 131 and the fore

section 125. The fore section is of a length that

allows its face 203 to abut the ram's inside face 201.

Whlen high pressure ai- is exposed to sub-

chamber 34 through spool valve 31, same moves through

port 205 past catch ring 139 into the interior 136

the ram 19. When the ram 19 is in an intermediate extended attitude as illustrated in Figure 7, this air pressure keeps the telltale rod 32 extended outwardly beyond the gun's housing 11 (as shown in Figure 7) to indicate that feedstock recharging is not yet permitted because of the differential air pressure force exerted on the telltale 32, the pressure in sub-chamber 34 being subst.alially greater than ambient. However, as the ram 19 moves forwardly, is extended, the catch ring 139 (which is press fit into seat 140 defined in face 111 of piston head 104) engages annular surface 138 on the circular plate 135, thereby pulling the telltale rod 32 inwardly into the motor chamber 105. Thus, and when the ram 19 has reached the attitude illustrated in Figure 6, same indicates that feedstock recharging is permitted since the telltale rod's tip 129 will have disappeared into guideway 127.

The barrel 14 itself is of a cylindrical shape,

and should be fabricated of a material, stainless

steel, with a low thermal -nmductivity to establish a

high tLieperature gradient axially along its length. The

barrel is carried within the gun's housing 11 by being

trapped between the housing's two halves lla, lib, i.e.,

by being seated as at 16 in the heater block 17, by

being supported annular rib 98, and by being seated as

at 145 in housing 146 of the manifold chamber 96. The

housing's halves lla, lib are in the nature of castings

which include the pistol grip 13 and trigger guard

The manifold chamber housing 146 is interconnected by a

web 144 with the cooling chamber housing 147 (which hous-

ing 147 includes bracket 77 and the cooling chamber

the distribution bore 91 passing through the web 144,

Assembly plate 109 also defines the housing 146 for the

manifold chamber 96. The housing 123 for the spool valve

31 and the housing 128 for the motor chamber 105 are a

single casting, that casting and the plate 109 being held

to the two half castings lla, lib by means, not shown.

The two halves lla, llb of the housing 11 are

tied together at the top by bolt 148 as shown in Figures

1 and 5, and are tied together at the bottom by bolts

149 (which also hold the hopper 22 in place on the barrel

14 as shown in Figure 2) received in spacer wings 150

cast integral with the web 144 that defines distribution

bore 91 as shown in Figures 2 and 3. These machine bolts

148, 149 hold the housing halves Ila, llb together from

side to side. A tie rod bolt 151 is located on each side

of the barrel 14 in the same horizontal plane. Each tie

rod bolt 151 passes through load plate 152 that seats the

heater block 17 against the fore end 18 of the barrel 14,

each passes through an eer 153 defined on the side of the

housing 147 for the cooling chamber 90, each then passes

through a hole 154 in housing 146 and is in engagem:Lt

with a tapped hole 154A defined in plate 109 for the

manifold chamber 96 (see Figures 2 and The tie rod

I bolts 151, at the fore end thereof, also connect a

mounting bracket 155 to the interior assembly. The

nose section 156 of the gun's housing 11 is connected

to the housing halves ila, lb through bolt 157 which

holds that nose section to the mounting bracket, see

Figure 2. Note that the housing's nose section 156 is

seated on annular lip 160 defined by the leading edge of

the housing's halves lla, Ilb, see Figure 2.

The nozzle 29 protrudes through the nose section

156, and an insulating ring 158 is disposed between the

heater block 17 and the nose section at that point to

prevent heat transfer from the heater block to the hous-

ing 11. Further, and within the nose section 156 of

the housing 11, insulation 159 is wrapped around the

heater block's base 43 to maintain the heat within the

heater block 17 and to insulate the housing 11 from the

heaLer block.

That embodiment of the hand gun 10 adapted for

use when the feedstock is in pellet or powder form is

particularly illustrated in Figures 1-4, 6 and 7. As

shown in those Figures, and as mentioned before, hopper 22

is fixed to the gun's housing by bolts 149 that restrain

the hopper's side ears 162 (and, therefore, the hopper)

in operative combination with the barrel 14 over the charg-

ing port 21. The hopper 22 is in the configuration of an

open top mouth having interior bottom walls 163 flared

inwardly toward the barrel. These bottom walls 163 term-

inate adjacent the arcuate shaped charging port 21 so as to direct the powder or granules into the barrel 14.

The hopper 22 is provided with safety structure

in the form of lid 23 that cannot be opened unless the

ram 19 is fully retracted, and that prevents the ram

from being extended once the lid is opened. The safety

lid 23 includes a hopper cover 164 having a handle 165

along one edge, and a lip 166 along the other edge. The

lip 166 is adapted to cooperate with a rounded top edge

16/ of the hopper 22, thereby serving as a latching device

to maintain the lid closed as shown in Figure 3. The

front and rear edges of the cover 164 are each provided

with an arm 168 that extends downwardly adjacent the

barrel 14, see Figures 2 and 3. Each of these arms 168

is pivotally mounted to the same tie rod 151a that runs

axially in parallel fashion along the barrel, thereby

allowing the lid to pivot between closed and opened

attitudes under certain condition, compare Figures 3 and

4.

However, the lid's rear arm 168a is configured

differently than the lid's front arm 168b, see Figures

2-4. The rear arm 168a (located aft of the charging port

21) is provided with an abutment in the form of extension

169 configured as shown in Figure 3. The extension 169

has an inner edge 170 that is concave shaped to coincide

with the barrells configuration when the cover 1.64 is

closed (see Figure and has an outer edge or segment

171 adapted to move into the barrel's interior (through

slot 172 formed in the barrel 14 and located aft of

the charging port 21) when the cover is opened (see

Figure This extension or abutment 169, which is part

of arm 168a, is a safety device as it will be apparent

that the cover 164 cannot be opened (because the extension

169 cannot move into the barrel's interior) after the

ram's face 107 has passed the slot 172 defined in the

barrel, compare Figures 1 and 7. This,r.of course, means

the hopper's cover 164 can only be opened by an operator

when the ram 19 has been fully retracted as shown in

Figure 1, at which position the barrel's slot 172 is

exposed so that extension 169 can move into the barrel's

interior. Further, and when the cover 164 is opened for

recharging the hopper 22, the ram 19 cannot be extended

forward in the barrel toward intermediate positions

shown in Figures 6 and 7 because extension 1.69 acts as a

positive stop by engaging the ram's face 107. This

occurs, of course, because extension 169 is always

disposed interiorly of the barrel 14 when the cover 164

is open, see Figure 4,

That embodiment of the Land gun 10 adapted to

be charged with one slug at a time is illustrated in

Figures 9 and 10. As shown in Figure 9, there is no

hopper 22 when the gun 10 is adapted to be charged with feedstock slugs. I single slug 25 is simply loaded directly into the barrel 14 when the charging port's cover 26 is in the phantom line or open position illu- strated in Figure 9. Note, of course, that the charging port 208 must be sized to receive a slug having a general- ly cylindrical configuratton with an outside diameter no greater than the irside diameter of the barrel 14, i.e., the port 208 is not circular as was the case with charg- ing port 21 for the pellet or powder embodiment.

The cover 26 is pivotally mounted on tie rod

151a, and is spring 173 biased continually toward the

closed or solid line position shown in Figure 9. The cover

26 includes a lid 174 section and an elbow 175 section,

the lid section having an inner surface 176 that is con-

cave shaped coincide with the barrel's outer periphery

when the cover is closed. The cover 26 can only be

pivoted open (by gripping nose section 177) to the

phantom line position shown in Figure 9 when the ram 19

is retracted past the charging port 208 because the

cover's extension section 175 must be able to move

into the barrel's interior through the charging port as

the cover is open. Once the cover 26 has been closed, it

cannot be opened after the ram 19 passes the aft edge

178 of the charging port 208 because the ram itself will

prevent extension 175 from entering the barrel's interior.

I Further, the cover 26 cannot be reopened once a lug

has been placed through the charging port 21 into the

barrel 14 until the slug has passed the fore edge 179

of the charging port; this because the cover's extension

175 would contact the slug if opening of the cover was

attempted.

That embodiment of the hand gun 10 adapted to

be charged through use of a multiple slug turret 27 is

illustrated in Figures 11 and 12. The turret 27 includes

cylinder 182 having three pockets 185, the cylinder being

mounted for rotation on bolt 184. The bolt 184 is

threaded into tapped hole 183 in housing 146 for the man-

ifold chamber 96, and is received in hole 186 in frame

section 187. Note that the cylinder 182 rotates on

axis 188 that is parallel to the barrel's axis

the cylinder's rotational axis 188 also being parallel

to the slug's axes 189 when same are seated in pockets

185. Note, also, in this multiple slug turret 27

embodiment that the turret pockets 185 function as a

rearward extension of the barrel (the barrel's aft end

190 stops forward of the turret and is seated as at 191

in frame section 187. Major bores '92a, !92b in the

frame section 187 are axially aligned with the barrel 14

and the ram 19, thereby presenting a single barrel con-

figuration in cooperation with successive pockets 185 in

cylinder 182.

Cylinder 182 is spring 193 loaded against the

front face 194 of frame sect'- n 146, and a detent 195

type latch is formed on that face 194 to cooperate with

depression 196 on the cylinder. This detent 195/depres-

sion 196 type latch functions to maintain the cylinder

182 in proper operating attitude where a slug's center-

line 189 is coaxial with the centerlines of the barrel

and ram. Spring clips 197 set in grooves 198 adjacent

each pocket 185 maintain the slugs 25 in seated engage-

ment with the cylinder 182, and insure alignment of the

slugs with the barrel 14 when each is turned into c~ial

alignment therewith.

The turret 27 cannot be rotate2 relative to

the barrel 14 unless the ram 19 is in the totally

retracted position shown in Figure 12. This for the

reason, of course, that ram 19 extends into a pocket 185

of the cylinder 182 during use of the gun 10. Oace the

ram has been fully retracted, and if the slug previously

within the charging port 21 area has been pushed past

fore edge 199 of the frame section's charging port 209,

then the cylinder 182 can be manually rotated by an

operator to place a new slug 25 in axial alignment ws'h

the gun's barrel and ram. Of course, the exposed pocket

185 that has been previously emptied may then be refilled

with a new slug by the operator simply by pressing same down into that pocket beyond :spring clips 197. Note that, even when all pockets 185 are emptied of slugs 25, it is still not possible for an operator to present hi,, fingers into the barrel because tl- turret 27 also functions as a revolving door that always keeps the barrel's interior closed to the environment.

Detailed Operation

In connection with operation of the hand gun

illustrated, the barrel 14 thereof is first filled with

a charge of thermoplastic material, a hot melt

adhesive; this charge may be made in either powder or

pellet form, or in slug form. If powder or pellets are

used as the feedstock, the hopper 22 and safety lid 23

are used in combin&tion with the barrel, see Figures 1-4,

6 and 7. If slugs are used as the feedstock, and if the

gun is of the single slug type, a safety cover 26 is

used as shown in Figures 9 and 10; if the gun is of the

multi-slug type, a safety turret 27 is used as illus-

trated in Figures 11 and 12.

ihen pellets 210 or powder is used as the

feedstock, the ram 19 must be in the fully retracted

attitude prior to opening the hopper's cover 164 and

charging the barrel 14, see Figure 1. The hopper's

cover 164 is then pivoted counterclockwise (see Figure 3)

on tie rod bolt 151a by grasping handle 165 and disengaging detent 166 from the hopper's shoulder 167.

Such a pivotal or lid opening motion is permitted when

the ram 19 is retracted because extension 169 of the arm

168a can move into the barrel's interior through

vertical slot 172, see Figure 4. In this open cover 164

attitude the powder or pellet feedstock is poured into the

hopper 22, a first charge of same passing through the

barrel's charging port 21 into the barrel 14, and the

hopper then being filled to the rim for further charges.

The cover 164 is then pivoted closed until detent 166

latchingly engages rim 167 of the hopper itself, the

stop or extension 169 thereby being withdrawn out of the

barrel interior. It will be recalled that the cover 164

cannot be opened once the ram 19 begins to extend because

extension 169 of the lid's arm 168a will no longer be

movable into the barrel's interior through vertical

slot 172. Thus, the hopper's cover 164 cannot be opened

to expose the charging port 21 if the ram 19 is forward

in an operating position and, conversely, the ram

cannot be moved forward if the hopper's cover is open.

Further, once the cover 23 is open, extension 169 acts

as a limit stop to prevent forward motion of the ram 19.

This forces the operator to go through the proper feed-

stock charging sequence so that he cannot get his finger

caught in the barrel 14 by the ram 19.

When the single slug version of the hand gun

is to be charged, the safty cover 26 must be pivoted

counterclockwise (see Figure 9) about tie rod 151a

-gainst the bias of spring 173 into the phantom line

position illustrated in Figure 9. In that open attitude,

the extension 175 of the cover 26 extends into the barrel

barrel's interior through charging port 208. As with the

hopper cover 23 embodiment, such is only possible when

the ram 19 is fully retracted, the safety cover 26

can only be opened when the ram is fully retracted. ,qhen

the cover 26 is opened, a slug 25 is positioned within

the barrel 14 through the charging port 208. Note that

the cover 26 and barrel 14 more or less difine a V-shaped

funnel in cross section to guide the slug into place

within the barrel, the cover snapping closed (because

of the spring 173 bias) over the slug once the slug is

fully within the barrel. The cover 26 cannot be opened

when the ram 19 is partially or fully extended in the

barrel because the ram intercepts extension 175 as it

is pivoted toward the barrel's interior. Further, if

there is still a slug within the charging port 21 area,

the lid cannot be opened either because of the fact that

the extension 175 extends the length of the lid. Further,

once cover 26 is open, extension 175 acts as a limit

stop to prevent forward motion of the ram 19. As with

the hopper cov-r 23 embodiment, this structure forces the

operator to go through the proper feedstock charging sequence so that he does not get his finger caught in the barrel by the ram 19.

When the multi-slug version of the hand gun

is to be charged, the cylinder 182 is simply rotated

about axis 188 with a slug 25 being inserted into each

pocket 185 of the cylinder, see Figures 11 and 12, The

slugs 25 are retained in successive pockets 185 by spring

clips 197 fixed to the cylinder 182. The cylinder 182,

after being filled, is rotated until a slug 25 is rotated

th 3h charging port 209 until it is positioned in

axial alignment within the barrel 14. Axial alignment

of the slug 25 and barrel 14, even though hidden from

the operator's view, is insured because of the detent

195/ depression 196 latch device. Of course, the turret

27 cannot be rotated once the ram 19 has been partially

extended because the ram passes through the cylinder's

pocket 185 that carries the slug 25 in process. Further, the ram 19 cannot be extended unless a pocket 185 is

axially aligned with ram 19. No special safety structure

is required in this embodiment because it is inherent in

the turret's structure. Access by an operator's fingers

into the barrel 14 is prevented at all times since the

cylinder's configuration, even when the gun 10 Is making

use of the last slug in the cylinder 182, always closes

the barrel's interior to the environment.

As mentioned, the ram 19 must be fully

retracted to allow charging of the barrel 14 through the

charging port 21 with either powder, pellets or slug

type feedstock. Motion of the ram 19 is controlled by

spool valve 31 as manually positioned through use of

handle 35. The spool valve 31 is hollow (because of

transfer bore 120) so that the spool valve acts not only

as a valve to direct flow to either port 118 or port 119,

but also as a means of transmitting pressu'rized inlet

air from the manifold chamber 96 to the sub-chamber 34

through bore 120 when it is desired to extend the ram.

The spool valve 31 is set up so that the sense

of direction of operation of the control valve's handle

is the same as the direction of ram 19 travel.

Retraction of the spool valve 31 into that attitude shown

in Figure 7 causes the ram to be retracted as pressur-

ized inlet air from manifold chamber 96 is directed through

port 119 into sub-chamber 38 of the pneumatic motor

This forces the piston head 104 rearwardly with exhaust

air in sub-chamber 34 being passed through port 118 into

spool valve bore 113 and then out through slot 122 to the

atmosphere. Discharge of the exhaust air from sub-chamber

34 is diffused as it passes into the atmosphere because

it exhausts between handle 35 and the housing 123 fir

the spool valve chamber, thereby preventing possible

injury to an operator from the air blast. When it is

CI

desired to extend the ram, the spool valve's handle

is stroked forward so that pressurized inlet air from

manifold chamber 96 is directed through transfer bore

120 and through port 118 into sub-chamber 34. This forces

piston head 104 forwardly with the exhaust air from sub-

chamber 38 being passed to atmosphere through port 119,

spool valve bore 113 and out through slot 122. As the

exhaust air passes out the slot 1?2, it, too, is baffled

by the handle

When the ram 19 is retracted, the inside face

201 of ram 19 contacts fore end 202 of telltale rod 32,

see Figure 7. As the ram 19 retracts, therefore, the

telltale rod 32 is forced aft until the telltale rod

32 stops against the collar 134 on the housing 128 for

the motor chamber 105 (which in turn stops the piston

head 104), thereby visually exposing the telltale rod's

tip 129 to an operator and locating the ram 19 in the

charging attitude. As the ram 19 is extended or moved

forward, it will be recalled that pressurized inlet air

is in sub-chamber 34 and this pressurized air passes

into the hollow interior 136 of the ram 19. Because of

the pressurized air acting on telltale rod 32, the rod

will not move forward toward the gun's nozzle 29 end

until catch ring 139 actually engages flange 135. In

other words, and prior to catch ring 139 engaging flange

135, if an operator poshed inwardly on the telltale rod

32 it would always pop back out. Thus, the catch ring

139 interengages the telltale rod's flapge 135 as the

ram 19 reaches an intermediate extended position and,

thereafter, pulls the telltale rod inwardly with it as

the ram 19 continues ;o move forward, see Figure 6. Once

the tip 129 of the telltale rod 32 disappears into the

gun housing's interior, same visually indicates to the

operator that recharging of the barrel 14 is permissible

since the ram's face 107 will have passed the fore edge

204 of charging port 21, ser Figure 6.

ihen the ram 19 moves forward under the press-

urized inlet air in sub-chamber 34, same compresses the

powder or pellets, or slug into engagement with the

frusto-conical portion 44 of the heater block 17,

Generally speaking, 40-60 psig in the sub-chamber 34

has been found adequate to provide the necessary hydraulic

pressure for the usual high melt adhesive in commerce

today. Indeed, certain high melt adhesives can be

adversely affected by too great a hydraulic pressure in

the sinse that they may tend to flow even though cold;

such uould tend to cause binding of the ram 19 within the

charging port 21 area of the barrel 14 and the genera-

tion of high radial forces creating large friction

forces between the feedstock and the barrel 14.

As the feedstock moves into proximity with the

frusto-cone 44, it is melted beginning at a solid/melt

interface 102. The frusto-cone 44 configuration is

highly effective in that the cones face 47 presents a

large surface area for melting purposes relative to the

cross sectional area of the barrel 14, in that it provides

a consistent thermal gradient along its axis from heater

block 47 to face 47, because of the heater elements

being in the heater blocks base 43, and in that the

molten material flows away from the interface 102 around

the cone's sides 48 as subsequent feedstock is moved up

toward the frusto-cone. Thus, as the feedstock is pushed

toward the frusto-cone 44, the molten feedstock 212 is

flowed radially outward from the cone's axis, and is then

collected in and directed through the annular passage

between the frusto-cone's sides 48 and the barrel 14.

The frusto-cone's sides 48 tend to flare both the molten

solid feedstock out against the inner wall of the barrel

14 where a dam or interface 102 is formed because that

wall has a steep thermal gradient over it. The wedging

action of the frusto-cone 44 coupled with the chill

on the barrel's outer periphery, in effect, provides the

solid/melt interface 102/e.l th is retained just aft

of the heater block 43. This self-damming or interface

102 forming function is particularly critical (and is

-51-

.1 accomplished) even with slug type feedstock where the slugs are not of a good initial fit with the barrel.

This interface 102, and the maintenance of same just

aft of the heater block prevents melt back into the

charging port 21 area of the barrel 14 and allows the use

of the high hydraulic pressures which are needed to

flow the more viscous high performance adhesives out of

the solid/melt interface promoting good flow rates and

allowing higher melt rates.

As previously noted, the annular cooling

chamber 90 materially aids in maintainfig the)solid/melt

interface 101 just aft of the heater block 43 as it is

through use of such that the thermal gradient over the

barrel's wall is established. Although there is not too

much of a melt back problem even with a relatively

warm barrel 14 wall as long as the powder or pellets

or slug continually move through the gun, melt back

does become a problem when the gun's discharge valve is

closed and no feedstock is being dispensed, at a

steady state soaking condition, such as would occur

during feedstock recharging or breaks in the work day.

The essence of the melt back problem is that the solid/

melt interface 102 tends to travel backward through the

barrel 14 toward the charging port 21 area, such is

prevented by the cooling chamber 90, the coolant being

provided by a portion of the pressurized inlet air

introduced into the distributor bore 91 through air

j line 94, that air passing bv choked flow through port 92 into the cooling chamber 90 so as to produce a relative cold coolant about the barrel 14 just aft of the frusto- cone's face 47. Further, the fact that housing wall 98 of the cooling chamber is in direct thermal contact with the outside of the barrel 14 also tends to reduce heat transfer back along the barrel. In addition, the cooling air is exhausted from chamber 90 through annular port 100 and directed axially forewxard along the outside surface of barrel 14 toward heater block 43, providing additional cooling of the barrel. Note that the wall thickness of barrel 14 is kept to a minimum to first reduce the heat transfer away from heater block 43 and, second, to reduce the thermal resistance radially to ease cooling of the feedstock circumference. The location of the cooling chamber 90 just aft of the frusto-cone's face

47 is about as far forward as it is desirable to have the

cooling chamber. Any further forward and the effect is

one of putting heat into the system behind or aft of the

cooling area. Further, it is desirable not to have the

cooling chamber 90 any further back along the barrel 14

because it is desirable to minimize that length of the

barrel which is hot. Of course, for a given air pressure

available through the line 94, the size of the port 92

.controls the flow rate into chamber 90. In establishing

the choked flow state for the maximum cooling effect, it

is necessary that the pressure in distributor bore 91, i be in the ratio of 1.92 to ambient and that the majority of the pressure drop occur across port 92.

After the feedstock has turned molten, it is

directed into the discharge valve bore 50 through heater

block bore 33, the melt 212 being forced from the barrel

through top 51 and bottom 52 ports. The molten feedstock

is discharged when desired by an operator through opera-

tion of a trigger assembly 36 that cooperates with the

discharge valve 28. In use, and as the trigger 37 is

drawn rearwardly by the operator's index finger, cup 69

is drawn rearwardly against the forward push of major

spring 68. This frees the cup 69 from abutting engage-

ment with the aft end 67 of valve stem 55. This, in

turn, allows hydraulic pressure on the valve head 56

(in combination with the spring assist from bellows seal

if that is used, or in combination with the spring

essist from that embodiment illustrated in Figure 8 if

that is used) to lift the valve head 56 off the valve

seat 57. .hen valve head 56 lifts off the valve seat

57, molten feedstock discharges through orifice 58 in

nozzle 29. That is, molten feedstock 212 will issue

from the gun's nozzle 29 only if the melt pressure

within the valve bore 50 is sufficient to cause the valve

stem 55 to move rearwardly along axis 53. Then such

occurs, and as long as the trigger 37 is retracted by

the operator's index finger, .olten feedstock will

issue from the nozzle 29 onto a workpiece as desired.

14hen ,s desired to terminate issuance of

molten feedstock from the nozzle 29, the trigger 37 is

simply released. Because major compression spring 68

creates substantially greater pressure than the hydraulic

pressure (and, also, greater pressure than the hydraulic

pressure in combination with the bellows seal 60 pressure

and/or the minor spring 70 pressure), the spring loaded

abutment 69 is pushed back into contact with the valve

stem's aft end 67. This, of course, causes the valve

head 56 to once again be seated on the valve seat 57 and,

thereby chokes off the flow of molten feedstock. It is

to be noted that the discharge valve 28 is actuated

independently of the trigger assembly 36 once the

spring loaded abutment 69 has been withdrawn from abutt-

ing contact with the valve stem 57. No matter how hard

an operator may deprcss the trigger, it will not mechan-

ically bear on the discharge valve 28 components and,

therefore, cannot cause damage to any valve 28 part

especially, the s-r ve bellows seal

The compression spring 68 is of a strength

such that above a predetermined pressure, 400 psig,

and even with the spring loaded abutment 69 contacting

the valve stem's aft end 67, the hydraulic pressure in

the discharge valve bore 50 (in combination with the

bellows seal pressure and/or in combination with the minor

spring 70 pressure, if either is 'ised) will provide sufficient force to overcome the compression spring 68 so as to force the discharge valve 28 open. Thus, and if for any reason the system becomes blocked and excess- ively high pressure starts to develop in the discharge valve 28 area, the discharge valve will be self-relieving and allow the pressurized molten feedstock to exhaust out the nozzle 29.

Claims (1)

1. The claims defining the invention are as follows:

   In a device adapted to translate a feedstock

   such as a thermoplastic adhesive from a solid state to

   a molten state, the improvement comprising

   a barrel having a charging port,

   a ram reciprocable in said barrel, said ram

   being adapted to force the feedstock toward the fore end

   of said barrel, and

   a heater block at least partially configured in

   a tapered surface located interiorly of said barrel at

   the fore end thereof, the axis of said tapered surface

   being aligned generally parallel to the axis of said

   barrel and being oriented in said barrel such that the

   tip of said tapered surface faces said ram so as to

   provide initial thermal contact with the feedstock at

   said tip.

   An improvement as set forth in Claim 1 wherein

   said barrel is of a cylindrical cross-sectional config-

   uration, and wherein said tapered section is of a circular

   cross-sectional configuration, the major diameter of said

   tapered section being approximately equal to the inside

   diameter of sa qrrel.

   An improvement as set forth in Claim 1 wherein

   said heater block includes a base formed integral with

   said tapered section.

   -bII-

   I

   An improvement as set forth in Claim 3

   including

   heater means in said base for supplying heat

   to said base and said tapered section.

   An improvement as set forth in Claim 3 wherein

   said base also defines a discharge bore that communicates

   with the interior of said barrel through at least one

   port in said heater block adjacent the inside periphery

   of said barrel, and further including

   a discharge valve in said discharge bore for

   controlling the discharge of molten feedstock form said

   device.

   An improvement as set forth in Claim 5 includ-

   ing

   a movable spring loaded abutment adapted

   continuously to bias said discharge valve closed except

   when said abutment is removed from abutting engagement

   with said valve, said abutment being retracted from

   abutting contact with said valve, to allow said valve

   to open when molten feedstock discharge is desired, and

   said abutment being allowed to return into abutting

   engagement with said valve to spring bias same closed

   when molten feedstock discharge is not desired,

   An improvement as set forth in Claim 6 wherein

   said discharge valve is hydraulically unbalanced, said

   valve being opened at least partially due to hydraulic

   pressure of molten feedstock in said discharge bore after

   said spring loaded abutment has been removed from

   abutting engagement with said valve.

   An improvement as set forth in Claim 6 includ-

   ing minor spring means to assist opening of said discharge

   valve after said spring loaded abutment has been removed

   from abutting engagement with said valve, said minor

   spring means having a strength less than the spring loaded

   abutment's major spring means.

   An improvement as set forth in Claim 6 wherein

   said discharge valve includes a valve stem fixed to a

   valve head, said valve stem extending outwardly of said

   base through a valve stem port therein, and wherein said

   spring loaded abutment is located exteriorly of said

   base, and including

   a static bellows t see' fixed to one of

   said valve stem and said valve head at one end and to

   said base at the other end so as to prevent leakage of

   molten feedstock through said valve stem port.

   An improvement as set forth in Claim 9

   including minor spring means to assist opening of said

   discharge valve after said spring loaded abutment has

   been removed from abutting engagement with said valve,

   said minor spring means having a strength less than the

   spring loaded abutment's major spring means, and said

   minor spring means being provided by placing said bellows

   seal under slight tension in that attitude where the

   discharge valve is closed.

   (11) An improvement as set forth in Claim 9 includ-

   ing minor spring means to assist opening of said discharge

   vTive after said spring loaded abutment has been removed

   from abutting engagement with said valve, said minor

   spring means having a strength less than the spring

   loaded abutment's major spring means, and said minor

   spring me-ns being provided by a compression spring

   exteriorly of said base that is interconnected with said

   valve stem.

   (12) An improvement as set forth in Claim 6 including

   a trigger assembly having a trigger connected

   to said spring loaded abutment, said spring loaded

   abutment being retracted from ab'-tting contact with said

   valve when said trigger is actuated.

   (13) In a device adapted to translate a feedstock

   such as a thermoplastic adhesive from a solid state to

   a molten state, the improvement comprising

   a heater block disposed at the fore end of a

   barrel, said heater block including anose portion that

   extends interiorly of the barrel in axial alignment

   therewith, said heater block also defining a discharge

   bore that communicates with the interior of said barrel,

   a hydraulically unbalanced discharge valve

   controlling the discharge of molten feedstock from said

   device, and

   a movable spring loaded abutment adapted

   continuously to bias said discharge valve closed except

   when said abutment is romoved from abutting engagement

   with said valve, said abutment being retracted from

   abutting contact with said valve to allow said valve to

   open due to hydraulic pressure within said discharge

   bore when molten feedstock discharge is desired, and

   said abutment being allowed to return into abutting

   engagement with said valve to spring bias same closed

   against the hydraulic pressure when molten feedstock

   discharge is not desired.

   (14) An improvement as set forth in Claim 13

   wherein said hydraulically unbalanced discharge valve

   includes a valve stem fixed to a valve head, said valve stem extending outwardly of said base through a valve stem port therein, and wherein said spring loaded abutment is located exteriorly of said heater block.

   An improvement as set forth in Claim 14

   including

   a static bellows type seal fixed to one of

   said valve stem and said valve head at one end and to

   said heater block at the other end so as to prevent

   leakage of molten feedstock through said valve stem port.

   (16) An improvement as set forth in Claim 13 wherein

   said hydraulically unbalanced discharge valve is provided

   with a minor spring assist, said minor spring assist

   adapted to oppose the spring loaded abutment's major

   spring to aid in opening said discharge valve when said

   spring loaded abutment is removed from abutting engage-

   ment with said valve.

   (17) An improvement as set forth in Claim 16

   wherein said hydraulically unbalanced diqcnarge valve

   includes

   a valve stem fixed to a valve head, said valve

   stem extending outwardl of said base through a valve

   stem port therein and a static bellows type seal fixed to one of said ralve stem and said valve head at one end and to said heater block at the other end so as to prevent leakage of molten feedstock through said valve stem port, and wherein said spring loaded abutment is located exteriorly of said heater block, and wherein said minor 3pring is in the nature of a compression spring located exteriorly of said heater block and interconnected with sai6 valve stem.

   (18) An improvement as set forth in Claim 16

   wherein said hydraulically unbalanced discharge valve

   includes

   a valve stem fixed to a valve head, said valve

   stem extending outwardly of said base through a valve

   stem port therein, and

   a static bellows type seal fixed to one of

   said valve stem and said valve head at one end and to

   said heater block at the other end so as to prevent

   leakage of molten feedstock through said valve stem port,

   and

   whereir said spring loaded abutment is located

   exteriorly of said heater block, and

   wherein said minor spring assist is provided

   by placing said bellows type seal in tension when said

   discharge valve is closed.

   -f3-

   (19) An improvement as set forth in Claim 14

   including

   a trigger assembly having a trigger connected

   to said spring loaded abutment, said spring loaded

   abutment being retracted from abutting contact with said

   valve when said trigger is actuated.

   An improvement as set forth in Claim 19

   wherein said spring loaded abutment and valve stem are

   adapted to move in coaxial linear paths, and wherein said

   trigger is connected with said spring loaded abutment by

   a lost motion slot so that arcuate motion of said trigger

   does not violate the linear motion of said spring

   loaded abutment.

   (21) In a device adapted to translate a feedstock

   such as a thermoplastic adhesive from a solid state to

   a mo3cen state, the improvement comprising

   a barrel, and a heater bi.ock located at the

   fore end of said barrel, and

   an annular cooling device disposed about the

   outer periphery of said barrel just aft of said heater

   block and adapted to direct a continuous coolant flow

   about said barrel, said annulAr cooling device serving

   to maintain a substantial axial thermal gradient along

   the length in said barrel so as to maintain a solid/melt

   interface inside the barrel adjacent to said heater block.

   (22) An improvement as set forth in Claim 21

   wherein said annular cooling device is in the nature of

   an annular chamber, same being provided coolant from a

   fluid source.

   (23) An improvement as set forth in Claim 22 wherein

   the fore wall of said cooling chamber ip sized to create

   an annular gap at said barrel's outer periphery, thereby

   providing an annular port through which the coolant can

   escape around the forward end of said barrel.

   (24) An improvement as set forth in Claim 22 wherein

   said pneumatic source is a single inlet air line, and

   includi..,

   a ram driven by a pneumatic moo,, aic

   inlet air line also serving to power said pneumatic

   motor for the gun's ram.

   In a device adapted to translate a feedstock

   such as a thermoplastic adhesive from a solid state to

   a molten state, the improvement comprising

   a barrel having a ram axially extendable and

   retractable therein,

   a ram motor having a piston head located within

   a motor housing, and

   control valve means adapted to alternately deliver and exhaust motive fluid with respect to at

   .0 least one face of said piston head, said piston head

   being in intimate thermal communication with the feedstock

   contacting face of said ram.

   (26) An improvement as set forth in Claim

   wherein the feedstock contacting face of said ram and

   said piston head are connected by a thermally conductive

   hollow member.

   (27) An improvement as set forth in Claim 25 wherein

   said control valve is in the nature of a spool valve

   contained in said motor housing, said spool valve having

   a transfer bore axially disposed therethrough, the oppos-

   ing end faces of said spool valve being of equal area.

   (28) An improvement as sat forth in Claim 27

   wherein said spool valve is aligned axially parallel

   with said barrel, stroking or said spool valve forward

   serving to positively drive said ram within said barrel

   in the forward direction, and stroking of said spool

   valve rearward serving to drive said ram in the aft

   direction.

   (29) An improvement as set forth in Claim 27 includ-

   ing an exterior member fixed to said spool valve, said

   c member extending through the exhaust porting from said motor and serving to diffuse the exhaust as same issues from said motor.

   In a device adapted to translate a feedstock

   such as a thermoplastic adhesive from a solid state to

   a molten state, the improvement comprising

   a ram axially extendable and retractable

   within a barrel, and

   a telltale cooperatively associated witn said

   ram that indicates when recharging of said barrel should

   take place, the indication being triggered by a specific

   extended location of said ram inside said barrel.

   (31) Anr improvement as set forth in Claim 30 wherein

   said telltale extends exteriorly of the gun's housing,

   said telltale being movable relative to said ram, and

   said telltale being mechanically actuated by said ram

   so as to withdraw sai telltale interiorly of the gun's

   housing as baid :ram is extended to that location within

   said barrel where recharging of the device should take

   place.

   (32) An improvement as set forth in Claim 31

   wherein said telltale is a so picked up by said ram at

   a specific point of ram retraction, said telltale bein carried with said ram until said ram is in the fully retracted position at which point said telltale extends exteriorly of the gun's housing.

   (33) An improvement as set forth in Claim 31 wherein

   said telltale is not actuated by said ram until said

   ram has been extended past the point at which charging

   can take place.

   (34) An improvement as set forth in Claim 31. wherein

   said ram is directly connected with a ram motor, said

   ram motor having a piston head located within a housing

   that divides said housing into a sub-chamber which is

   exposed to a fluid pressure source so as to extend said

   ram in said barrel, and wherein said telltale presents

   a first exterior surface exposed to the atmosphere and

   an opposing second interior surface exposed to said

   source as said ram is extended so as to maintain said

   telltale's tip exteriorly of the gun's housing until

   said telltale is actuated by said ram.

   An improveent as set forth in Claim 34 wherein

   said ram defines a hollow interior, and wherein said

   telltale is coaxially received into said ram's interior.

   !I 1

   I

   A

   ~fl 2II.2

   jfljj I.' 11.8 1.4

   MICROCOWY RESOLUTION TEST CHART BUREAUOF STANDARDS-963-A NATIOJNAL

   I (36) In a device adapted to translate a feedstock

   such as a thermoplastic adhesive from a solid state to

   a molten state tne improvement comprising

   a barrel having a charging port,

   a ram axially located within said barrel, said

   ram being adapted to move within said barrel between a

   fully retracted attitude aft of the charging port and a

   fully extended attitude fore of the charging port,

   a cover for said charging port, and

   a safety interlock cooperatively associated

   with said charging port's cover, said interlock prevent-

   ing exposure of said charging port for recharging unless

   said ram has been fully retracted and insuring that

   said ram will be retained in the fully retracted position

   while said charging port is exposed for recharging.

   (37) An iwprovemen as Get forth in Claim 36 wherein

   said feedstock is of a powder or pellet type, and include

   ing

   a hopper fixed over said charging port, said

   cover being adapted to close said hopper to the environ-

   ment, and

   an extension fixed to said cover, said extension

   being adapted to move into the barrel's interior as said

   cover is opened when said ram is fully retracted and to

   prevent said ram from being extended as long as said

   cover is opened.

   -l

   (38) An improvement as set forth in Claim 37 wherein

   said extension is adapted to move into and out of a

   slot in said barrel said slot being located aft of said

   charging port's aft edge.

   (39) An improvement as set forth in Claim 37

   wherein said charging port Ls of an arcuate configuration,

   and wherein said ram's face is flat and disposed trans-

   verse relative to said barrel's axis.

   (AO) An improvement as set forth in Claim 36 wherein

   said feedstock is of a slug type, and including

   an extension fixed to said cover, said

   extension being adapted to move into the barrel's

   interior as said cover is opened when said ram is fully

   retracted and to prevent said ram from being extended

   as long as said cover is opened.

   (41) An improvement as set forth in Claim 40 wherein

   said extension moves into and out of said barrel's

   interior through said charging port.

   (42) An improvement as set forth in Claim 36 wherein

   said feedstock is of a slu, type, said cover and safety

   interlock being in the nature of a slug feeder axially

   aligned with said barrel but spaced therefrom, said feeder

   -7 0-

   Tlvl .r Ama presenting at least one slug pocket adapted to be moved into and out of axial alignment with said barrel when said ram is fully retracted, thereby allowing a new slug

   :o be charged into said barrel.

   (43) An improvement as set forth in Claim 42

   wherein said slug feeder comprises a rotatable turret

   having multiple pockets, each pocket being adapted to

   receive a slug in axial alignment with said barrel, and

   each pocket being adapted to move into alignment with the

   barrel so that said slug is coaxial with said ram and

   barrel as said turret is rotated.

   (44) An improvement as set forth in Claim 43 wherein

   said slug turret includes a series of clips associated

   with each pocket, said clips being adapted to retain the

   slug in each pocket until the slug is pushed out of said

   pocket by said ram after the slug has been aligned

   interiorly of said barrel.

   An improvement as set forth in Claim 43 includ-

   ing a latch device adapted to restrain said turret in the

   exact location where a slug will be axially aligned

   interiorly of said barrel after rotation of said turret.

   (46) In a device adapted to discharge a liquid

   material through a nozzle, the improvement comprising

   a discharge valve having a valve head reciproc-

   able within a discharge bore, said valve head being

   adapted to raise off of and seat on a valve seat for

   controlling the liquid material discharge, and

   a movable spring loaded abutment adapted

   continuously to bias said valve head closed except when

   said abutment is removed from abutting engagement with

   said valve head, said abutment being retracted from

   abutting contact with said valve head to allow said

   discharge valve to open when liquid material discharge

   is desired, and said abutment being allowed to return

   into abutting engagement with said valve head to spring

   bias said discharge valve closed when liquid material

   discharge is not deisired.

   (47) An improvement as set forth in Claim 46 wherein

   said discharge valve is hydraulically unbalanced, said

   valve head being opened at least partially due to

   hydraulic pressu-e of liquid material in said discharge

   bore after said spring loaded abutment has been removed

   from abutting engagement with said valve head.

   (48) An improvement as set forth in Claim 46

   including minor spring means to assist opening of said

   valve head after said spring loaded abutment has been

   removed froT abutting engagement with said valve head,

   said minor spring means having a strength less than the

   spring loaded abutment's major spring means.

   (49) An improvement as set forth in Claim 46 wherein

   said discharge valve includes a valve stem fixed to said

   valve head, said valve stem extending outwardly of said

   base through a valve stem port therein, and wherein

   said spring loaded abutment is located exteriorly of

   said base and is adapted to bear on said valve stem.

   An improvement as set forth in Claim 46

   wherein said discharge valve includes

   a static bellows type seal fixed to one of

   said valve stem and said valve head at one end and to

   said discharge bore at the other end so as to prevent

   leakage of liquid material through said valve stem

   port, and

   minor spring means to assist opening of said

   discharge valve after said spring loaded abutment has

   been removed from abutting engagement with said valve,

   said minor spring means having a strength less than the

   spring loaded abutment's major spring means, and said

   minor spring means being provided by placing said bellows seal under slight tension in that attitude where the discharge valve is closed.

   (51) An improvement as set forth in Claim 49 includ-

   ing minor spring means to assist opening of said ,valve

   head after said spring loaded abutment has been removed

   trom abutting engagement with said valve, said minor

   spring means having a strength less than the spring

   loaded abutment's major spring means, and said minor

   spring means being provided by a compression spring

   exteriorly of said base that is interconnected with said

   valve stem.

   (52) An improvement as set forth in Claim 46 including

   a trigger assembly having a tUigger connected

   to said spring loaded abutment, said spring loaded

   abutment being retracted from abutting contact with said

   valve when said trigger is actuated.

   (53) A thermoplastic material dispensing apparatus

   adapted to convert a thermoplastic feedstock material

   from a solid state to a molten state and subsequently

   dispense said molten material, said apparatus including

   a barrel having a charging port,

   a ram reciprocable in said barrel, said ram

   being adapted to force the feedstock toward the fore end

   I iO:f v' i a

   of said barrel, and

   a heater block at least partially configured

   in a tapered surface located interiorly of said barrel

   at the fore end thereof, the axis of said tapered surfacb

   being aligned generally parallel to the axis of said

   barrel and being oriented in said barrel such that the

   tip of said tapered surface faces said ram so as to

   provide initial thermal contact with the feedstock at

   said tip.

   (54) The apparatus of Claim 53 wherein said barrel

   is of a cylindrical cross-sectional configuration, and

   wherein said tapered section is of a circular cross-

   sectional configuration, the major diameter of said

   tapered section being approximately equal to the inside

   diameter of said barrel.

   The apparatus of Claim 53 wherein said heater

   block includes a base formed ii*tegral with said tapered

   section.

   (56) The apparatus of Claim 55 which further includes

   heating means in said base for supplying heat

   to said base and said tapered section.

   (57) The apparatus of Claim 55 wherein said base

   N.

   also defines a discharge bore that communicates with the

   interior of said barrel through at least one port in said

   heater block adjacent the inside periphery of said barrel,

   and further including

   a discharge valve in said discharge bore for

   controlling the discharge of molten feedstock from said

   device.

   (58) A thermoplastic material dispensing apparatus

   adapted to convert a thermoplastic feedstock material from

   a solid state to a molten state and subsequently dispense

   said molten material, said apparatus including

   a ram axially extendable and retractable

   within a barrel, said ram exposing a charging port defined

   in said barrel when in its fully retracted position, and

   a telltale cooperatively associated with said

   ram that visually indicates to an operator when recharg-

   ing of said barrel should take place, the visual indica-

   tion being triggered by a specific extended location of

   said ram inside said barrel.

   (59) The apparatus of Claim 58 wherein said ram is

   substantially holl in configuration, and wherein said

   telltale hac a tip extending exteriorly of the gun's

   housing, said telltale being linearly movable relative

   to szid ram, and said telltale being picked up by said

   jy~ I*~L IY i x MIIS ram so as to withdraw said tip interiorly of the gun's housing as said ram is extended to that location within said barrel where recharging of the device should take place.

   The apparatus of Claim 59 wherein said telltale

   is also picked up by said ram at a specific point of ram

   retraction, said telltale being carried with said ram

   until said ram is in the fully retracted position at

   which point said telltale's tip extends exteriorly of

   the gun's housing.

   (61) The apparatus of Claim 59 wherein said tell-

   tale is not picked up by said ram until said ram has

   been extended past the forward edge of said cha':ging port.

   (62) The apparatus of Claim 59 wherein said ram is

   directly connected with a ram motor, said ram motor having

   a piston head located within a housing that divides

   said housing into a subchamber which is exposed to a

   fluid pressure source so as to extend said ram in said

   barrel, and wherein said telltale presents a first

   exterior surface exposed to the atmosphere and an opposing

   second interior surface exposed to said souree as said

   ram is extended so as to maintain said telltale's tip

   exteriorly of the gun's housing until said telltale is

   -(77- t

   I

   picked up by said ram.

   (63) A thermoplastic material dispensing apparatus

   adapted to convert a thermoplastic feedstock material

   from a solid state to a molten state and subsequently

   dispense said molten material, said apparatus including

   a barrel having a charging port,

   a ram axially located within said barrel, said

   ram being adapted to move within said barrel between a

   fully retracted attitude aft of the charging port and a

   fully extended attitude fore of the charging port,

   a cover for said charging port, and

   a safety interl :k cooperatively associated

   with said charging port's cover, said interlock prevent-

   ing exposure of said charging port for recharging unless

   said ram has been fully retracted and insuring that said

   ram will be retained in the fully retracted position

   while said .narging port is exposed for recharging.

   (64) The apparatus of Claim 63 wherein said feed-

   stock is of a powder or pellet type, and further including

   a hopper fixed over said charging port, said

   cover being adapted to close said hopper to the envirou-

   ment, and

   an extension fixed to said cover, said extension

   being adapted to move into the barrel's interior as said

   -,78 r

   N cover is opened when said ram is fully retracted and to prevent said ram from being extended as long as said cover is opened.

   The apparatus of Claim 64 wherein said extension

   is adapted to move into and out of a slot in said barrel,

   said slot being located aft of said charging port's

   aft edge.

   (66) The apparatus of Claim 63 wherein said feed-

   stock is of a slug type, and further including

   an extension fixed to said cover, said extensioni

   being adapted to move into the barrel's intexior as said

   cover is opened when said ram is fully retracted and to

   prevent said ram from being extended as long as said

   cover is openied.

   (67) A thermoplastic material dispensing apparatus

   adapted to convert a thermoplastic feedstock material

   from a solid state to a moltan state and subsequently

   dispense said molten material, said apparatus including

   a discharge valve having a valve head reciproc-

   able within a discharge bore, said valve head being

   adapted to raise off of anA seat on a valve seat for

   controlling the liquid material discharge, and

   a movable spring loaded abutment adapted

   i 4-7L- '~d continuously to bias said valve head closed except when said abutment is removed from abutting engagement with said valve head, said abutment being retracted from abutt- ing contact with said valve head to allow said discharge valve to open when liquid material discharge is desired, and said abutment being allowed to return into abutting engagement with said valve head to spring bias said discharge valve closed when liquid material discharge is not desired.

   (68) The apparatus of Claim 67 wherein said discharge

   valve is hydraulically unbalanced, said valve head being

   opened at least partially due to hydraulic pressure of

   liquid material in said discharge bore after said spring

   loaded abutment has been removed from abutting engagement

   with said valve head.

   (69) The apparatus of Claim 67 and further including

   minor spring means to assist opening of said valve head

   after said spring loaded abutment has been removed from

   abutting engagement said valve head, said minor

   spring means having a strength less than the spring

   loaded abutment's major spring means.

   The apparatus of Claim 67 wherein saic7discharge

   valve includes a valve stem fixed to said valve head,

   said valve stem extending outwardly of said base through

   .k a valve stem port therein, and wherein said spring loaded abutment is located exteriorly of said base and is adapted to bear on said valve stem.

   (71) The apparatus of Claim 67 which further includeq

   a static bellows type seal fixed to one of

   said valve stem and said valve head at one end and to

   said discharge bore at the other end so as to prevent

   leakage of liquid material through said valve stem port,

   and

   minor spring means to assist opening of said

   discharge valve after said spring loaded abutment has

   been removed from abutting engagement with said valve,

   said minor spring means having a strength less than the

   spring loaded abutment's major spring means, and said

   minor spring means being provided by placing said bellows

   seal under slight tension in that attitude where the

   discharge valve is closed.

   (72) A thermoplastic material dispensing apparatus

   adapted to convert a thermoplastic feedstock material from

   a solid state to a molten state and subsequently dispense

   said nolcen material, said apparatus including,

   a main frame,

   a barrel with a charging port suppotted by

   said frame,

   a heater and nozzle mounted at the fore and

   of said barrel, a ram reciprocable in said barrel, said ram being adapted to force the feedstock toward the fore end of said barrel, and said ram having appiston head located within a motor housing, said piston head reciprocable in said motor housing, and valve means disposed in said motor housing, said valve means controlling the flow of motive cooling fluid to and from said motor housing, said motive fluid positively driving and cooling said piston and ram within said motor housing in both fore or aft directions of reciprocation.

   (73) The apparatus as set forth in Claim 72 wherein

   said main frame comprises

   a fluid manifold, and

   passageways formed in said manifold for simul"

   taneously conducting motive cooling fluid to said motor

   housing and cooling fluid to the fore end of said barrel.

   (74) The apparatus set forth in Claim 72 wherein

   said ram has a hardened element secured to its forward

   end, said hardened element cooperating wit' said charging

   port in said barrel to form a shear, said shear being

   adapted to cut-off any excess feedstock material tending

   to block said charging port during forward movement of

   said ram.

   The apparatus ,et forth in Claim 72 wherein

   said piston head has a cross-sectional area which is at

   least three times greater than the cross-sectional area

   of said ram.

   (76) Thermoplastic feedstock melting means compris-

   ing a heating surface disposed within a feedstock trauisfer

   barrel, said heating surface configured to simultaneously

   imelt solid advancing feedstock and .~dially outwardly

   displace said soliu advancing feedstock into intimate

   contact with the interior sub:face of said feedstock trans-

   fer barrel, said transfer barrel having a substantial

   axial thermal gradient with decreasing barrel temperature

   upstream of said heating surface.

   (77) Thermoplastic feedstock melting means comprising

   a tapered surface heating member with decreasing surface

   temperature from base to tip, said tapered surface short-

   ened from its vanishing point tc the extent necessitated

   by the combination of surface heat flux and thermal cond-

   uctivity of said heating member material so that the tip

   temperature of said heating member is maintained at or

   above the feedstock softening point, said tip constitut-

   ing the initial thermal contact with the advancing

   feedstock.

   -83-

   j

   78. A hand gun device adapted to translate a feedstock such as a thermoplastic adhesive from a solid

   state to a molten state, comprising a handle grip, a

   barrel supported from said grip, said barrel having a

   charging port, a ram reciprocable in said barrel, said

   ram being adapted to force the feedstock toward the fore

   end of said barrel, and a heater block at least partially

   configured in a tapered surface located interiorly of said

   barrel at the fore end thereof, said tapered surface being

   oriented in said barrel such that an end tip of said tap-

   ered surface faces said ram so as to provide initial thermal

   contact with the feedstcck at said tip, said tapered surface

   of said heater block and the interior surface of said barrel

   defining therebetween a converging channel through which

   the feedstock is forced during passage toward said fore

   end of said barrel, said feedstock having a transition

   region in which it converts from the solid to the molten

   state, arj the improvement which comprises means for main-

   taining the said transition region at the point at which

   it contacts said barrel confined within said converging

   channel such that said barrel contact, :g portion of said

   transition region is subject to a force normal to said

   interior surface of said barrel and acts as a physical dam

   to prevent backflow of molten material along the inside

   surface of said barrel.

   79. In a device adapted to translate a feedstock such as a thermoplastic adhesive from a solid state to a

   molten state, the improvement comprising a barrel having a

   charging port, a ram reciprocable in said barrel, said ram

   being adapted to force the feedstock toward the fore end of said barrel, a heater block located in and extending gen- erally axially of said barrel, said heater block having a section flaring outwardly toward the fore end of said barrel, said barrel having an internal surface region adjacent to said outwardly flaring section of said heater block which is maintained at a temperature below the melt- ing point of said feedstock, so that said flaring section of said heater block is operable to flare the molten/solid feedstock interface out against the inner wall of said barrel within the axial extent of said outwardly flaring section of said heater block and effectively dams molten material against melt back outside of said internal surface region of said barrel.

   In a portable hand gun device adapted to

   translate a feedstock such as a thermoplastic adhesive

   from a solid state to a molten state, which device has a

   hand grip for supporting the device, the improvement which

   comprises a barrel supported from said hand grip, said

   barrel having a charging port, a ram reciprocable in said

   barrel, said ram being adapted to force the feedstock

   toward the fore end of said barrel, a heater block having a

   substantial.y imperforate section, said section continuously

   increasing in cross section toward a base section, said

   base section providing a hydraulic closure at one end of

   said barrel, and said barrel having an internal surface

   region adjacent to the axial extent of said heater block

   which is maintained at a temperature below che melting

   point of said feedstock.

   ,/1

   DATED this THIRD day of APRIL, 1974 NORBSON CORPORATION

   Patent Attorneys for tde Applicant SPRUSON FERGUSON